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Re: CULT: rhizome size vs bloom vs soil conditions vs climate

this is going to sound like an off beat question.  What kind of hay was the
If the hay was a legume... alfalfa or clover... and it had been that kind of
hay for many years... there might be an "abundance" of nitrogen in that
field.  I've heard that irises are heavy nitrogen feeders... if that's true,
it would stand to reason that a legume hay field might nourish the plant
aggressively enough that there is extra to store in the rhizomes.
It's only a guess...

--- On Fri, 7/25/08, Laurie Frazer <lauriefr@localnet.com> wrote:

From: Laurie Frazer <lauriefr@localnet.com>
Subject: [iris] CULT: rhizome size vs bloom vs soil conditions vs climate
To: iris@hort.net
Date: Friday, July 25, 2008, 10:45 AM

Hello All,

I have noticed an odd phenomenon in my iris beds this year, and I'm
still trying to figure out which of many factors are playing primary
roles here.

With my very short growing season, it often takes bearded irises of all
classes several years to settle in and start blooming regularly.

Several years ago, I created a new bed in iris-virgin soil (used to be
hayfield) which I stupidly and severely overfertilized at the time of
its conversion to irises.  This "hayfield bed" is in full sun and in
open, unprotected area, fully vulnerable to all climatic conditions.

My primary iris beds (also stupidly overfertilized years ago and still
trying to leach out the extra chemicals) are located over my septic
drainfield in an area behind the house protected on one side by the
house and on all other sides by a variety of taller trees, bushes, and
shrubby undergrowth.  These partially shaded beds have been growing
irises for about 12 yrs.

Neither the hayfield nor the primary beds have been fertilized in
years, and I have not provided any supplemental water to either of them
at all this year. Both beds were initially amended with essentially the
same things, and the primary beds have been dug and reamended a couple
of times over the years.  Both beds are planted on raised windrows to
improve drainage and reduce rot.  Both beds are fenced to reduce (but
not necessarily eliminate) animal traffic.

This year is the second year in a row when difficult climatic
conditions have had severe consequences in the iris beds, though the
stressors each year have been somewhat different.

Now here are the interesting observations I've made this year.  These
comments, btw, refer primarily to dwarf and median beardeds.  TBs
aren't even worth mentioning in a difficult year like this one.  In the
fully exposed, hayfield bed, there was fairly minimal bloom this year.
Many irises that started growing in early spring have since weakened,
sickened, and in some cases, died - I assume as a result of the
repeated climatic stresses to which they were subjected earlier in
spring.  There's been more of the enigmatic "scorch" in that bed
year than I have ever seen here - clumps losing all foliage while rzs
remain firm and apparently healthy looking.  What is even more
puzzling, though, is the rz size of the surviving irises in that bed.
They are HUGE!  They look like those West Coast lunkers so many
irisarians drool over.  I have NEVER managed to grow rzs even a tenth
that size here before.  Is it the fact that that bed was virgin soil
several years ago?  Or is it the full sun position?  I know it's not
extra water, cuz it hasn't gotten any more than average rainfall this

Meanwhile, back in the old soil of the shadier, protected primary beds,
bloom was much better on the MDBs and SDBs (poor bloom on most beardeds
taller than SDBs), there is NO scorch, losses are minimal, and the rzs
are tinier than I've ever seen them.  I mean, raisin tiny.  These beds
are in serious need of digging and reamending, because they are overrun
with grass and weeds of every description and haven't been dug in too
many years.  So, I'm not surprised by the rz sizes in those primary

I guess what I'm finding so surprising is not only the massive rz sizes
of the surviving irises in the exposed, hayfield bed, but also the
amount of dead and/or dying (NOT rotting) irises in that same bed vs
lack of same in the protected primary beds.  It would seem that in my
climate, at least MDBs and SDBs (with their reduced requirement for
full sun) do better in a growing location where they receive some
natural protection from the worst of the weather.  Even the taller
medians and talls are much healthier in the protected beds, though
their bloom potential certainly suffers without full sun.  And once
again, in my experience here in the Northland, mature rz size seems to
have nothing to do with either bloom or health of the plant.

Interesting year here.


Shadowood - http://lfrazer.com
The Irises of Shadowood - http://lfrazer.com/iris/
Wallplates With Panache - http://lfrazer.com/wallplates/

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